Errr... I do not allow pop-adverts on PPRuNe!
Are you sure it is from the PPRuNe web page that you are getting them? Are you using AOL or one of the 'nanny' ISP's to log on with? They sometimes force you to keep one of their windows open and who knows what they do in the background.
I use one advertising company for some banners but I definitely do not allow them to submit pop-ups. I detest pop-ups as much as the next person. I have never seen a pop-up ad whilst using PPRuNe and it would appear that only some of you are getting them which leads me to suspect that it is some other window you have open (although possibly reduced in size) that is causing you the grief.
Investigation continues.